[llvm-bugs] [Bug 52290] New: [SimplifyCFG] Hang/Assertion `IterCnt++ < 1000 && "Sanity: iterative simplification didn't converge!"' failed.

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=52290

            Bug ID: 52290
           Summary: [SimplifyCFG] Hang/Assertion `IterCnt++ < 1000 &&
                    "Sanity: iterative simplification didn't converge!"'
                    failed.
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: max.kazantsev at azul.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org

To reproduce: run "opt -simplifycfg -S" on the following test

; RUN: opt < %s -simplifycfg -S | FileCheck %s
; RUN: opt < %s -passes=simplifycfg -S | FileCheck %s

; FIXME: Fails due to infinite loop in iterativelySimplifyCFG.


define i32 @test(float %arg) gc "statepoint-example" personality i32* ()* @blam
{
bb:
  %tmp = call i1 @llvm.experimental.widenable.condition()
  br i1 %tmp, label %bb2, label %bb1

bb1:                                              ; preds = %bb
  br i1 undef, label %bb7, label %bb5

bb2:                                              ; preds = %bb
  %tmp3 = getelementptr inbounds i8, i8 addrspace(1)* undef, i64 16
  br i1 undef, label %bb6, label %bb4

bb4:                                              ; preds = %bb2
  call void @snork() [ "deopt"() ]
  unreachable

bb5:                                              ; preds = %bb1
  ret i32 0

bb6:                                              ; preds = %bb2
  br label %bb7

bb7:                                              ; preds = %bb6, %bb1
  %tmp8 = call i32 (...) @llvm.experimental.deoptimize.i32(i32 10) [ "deopt"()
]
  ret i32 %tmp8
}

declare i32* @blam()

declare void @snork()

declare i32 @llvm.experimental.deoptimize.i32(...)

; Function Attrs: inaccessiblememonly nofree nosync nounwind speculatable
willreturn
declare i1 @llvm.experimental.widenable.condition() #0

attributes #0 = { inaccessiblememonly nofree nosync nounwind speculatable
willreturn }

Originally result was hang (and it's same in product). I've added a sanity
assert and it now is failing. It happens due to infinite execution of
iterativelySimplifyCFG. The IR does not change between iterations, so maybe two
transforms are undoing one another.

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